Systems that involve the detection of light are used in a variety of contexts. In particular, systems that involve the detection and subsequent analysis of light are used in performing optical spectroscopic assays, including luminescence and absorption assays. These assays are used to characterize the components and properties of molecular systems, and recently have been used in high-throughput screening procedures to identify candidate drug compounds. Optical spectroscopic assays include fluorescence polarization (FP), fluorescence resonance energy transfer (FRET), fluorescence lifetime (FLT), total internal reflection (TIR) fluorescence, fluorescence correlation spectroscopy (FCS), and fluorescence recovery after photobleaching (FRAP), and their phosphorescence analogs, among others. Optical spectroscopic assays also include absorption assays.
Unfortunately, light detection systems suffer from a number of shortcomings. Such systems may be limited in range, so that they accurately detect light only within some relatively narrow range of intensities. Such systems also may require user intervention to alter the detection range, if the range may be altered at all. Such systems also may be limited to either discrete or analog detection, so that either they discretely count individual quanta or photons of light, or they integrate an analog value corresponding to such quanta, but they do not do both. Such systems also may require significant periods of time to make measurements. These shortcomings may be found singly or in combination, and these shortcomings may be particularly significant in the context of high-throughput screening, where it may be necessary to perform tens or hundreds of thousands of measurements per day.